Fabrication of high alloy steels, particularly stainles steel, in electric furnaces, has some difficulties in cases of high Cr and low C contents (less than 0.10% Carbon), due to high process temperatures required, and Cr loss in slag due to the high oxidation needed to reduce the carbon content. As a result of the high temperatures in the furnace there is a high consumption of refractory. Both factors, refractory consumption and chromium losses makes this way of production costly and inefficient.
An alternate method is based in the AOD process. The AOD process is a metallurgical method that consists of a vessel with an opening on top of the same, and a set of tuyeres that are located in the side wall, below the liquid level, and usually extended radially in horizontal position.
The AOD converter is usually fed with hot metal by an electric furnace. The hot metal contains generally 0.9-1.7% carbon. A mixture of oxygen and argon having a ratio of about 3 parts of oxygen to 1 part of argon is blown through the center tuyere while argon or air is delivered through the outer tuyere pipe as a coolant or shielding fluid. During the process cycle, the ratio of argon and oxygen delivered to the center tuyere is changed.
The AOD process has the following disadvantage:
(a) High cost as a result of refractory wear, and high argon consumption for cooling and shielding. PA1 (b) Low availability due to frequent shut downs for repair and maintenance.